7-Aminocephalosporanic acid (7-ACA), the core of many semi-synthetic cephalosporins, is conventionally manufactured chemically from cephalosporin C. The chemical process uses chemical reagents that are highly toxic and heavily pollute the environment and the chemical process is low in conversion rate, as the process requires multiple steps of reactions. Bio-process offers an attractive alternative for the production of 7-ACA. The bioconversion of cephalosporin C to 7-ACA is conducted in two steps: (1) cephalosporin C is first oxidized by D-amino acid oxidase to glutaryl-7-ACA; (2) the glutaryl-7-ACA is then cleaved at the bond between the glutaryl moiety and the 7-ACA moiety by glutaryl-7ACA acylase to 7-ACA. Rhodotorula gracilis and Trigonopsis variabilis are the two major sources of D-amino acid oxidase for industrial application. However, these enzymes are low in their catalytic activities for oxidizing cephalosporin C (Simonetta, et al., Biochim. Biophys. Acta, 914: 136-142 (1987); U.S. Pat. Nos. 5,453,374; and 5,208,155). It is, therefore, desirable for the industry to have a D-amino acid oxidase of higher catalytic activity to reduce the cost of the bioconversion of cephalosporin C to 7-ACA.